This invention relates to a tire and a tire and rim combination in which the tire may be collapsed in its uninflated state to assume smaller overall dimensions than the tire has in its inflated, operable shape. Such folding yields a smaller physical package than a standard tire to tire and rim combination which results in a savings of space and weight. The tire of this invention is particularly useful as a spare tire for passenger automobiles.
Due to the excellent performance record of tires over the past 20 years, the space tire is an automobile is now considered less of a necessity and a product that merely goes along for the ride in most instances. Considering the number of automobiles presently in use and the number of spare tires contained therein, the transportation of the spare tire represents a major wastage of natural resources, particularly fuel and raw materials. Much emphasis is now being placed on a tire designed specifically to be a spare tire with limited service capabilities that conserves space in the automobile, contains less raw materials, and most importantly, weighs less than a standard tire. Such a tire permits the design of smaller, lighter automobiles and represents a reduction of weight in an automobile. Such a reduction means a fuel savings because the automobile is simply carrying less weight.
Certain manufacturers have approached this problem in different ways, all of which have disadvantages. U.S. Pat. Nos. 3,347,300; 3,347,301; 3,347,964; 3,372,726; 3,393,725; 3,394,751; 3,421,566; 3,570,572; 3,394,750; 3,400,746; and 3,506,748 represent one such method; U.S. Pat. Nos. 3,657,039; 3,833,042 and 3,540,510 represent another method and U.S. Pat. No. 3,610,310 represents yet another method.
The method and product exemplifying the first approach has a major disadvantage in that the tire is cured in a bladderless state; that is, in the curing or vulcanizating operation no internal member is inserted into the tire to encase the steam that is utilized inside the tire to obtain vulcanization. Bladderless curing operations are notoriously difficult to accomplish by mass production techniques and the rate of factory rejects always is extremely high in such operations. Additionally, due to the cured fold in the tire sidewall and the cured configuration of the bead area (see U.S. Pat. No. 3,347,300), the lower sidewall area (the area immediately adjacent the tire bead) of the tire of this approach is subjected to a great deal of buckling on inflation which creates stresses they may result in performance problems in this area of the tire. Additionally, the cured, folded sidewall configuration creates inspection problems in the cured tire as it is very difficult to visually inspect the inside of the tire for possible building or curing defects with the folds present.
The second approach does not employ bladderless curing but utilizes a standard type curing operation wherein a bladder is inserted in the tire prior to vulcanization. However, due to the cured configuration of the bead area, this approach does not eliminate the buckling and resulting stress problem in the lower sidewall area of the tire.
Little is known of the third approach beyond that disclosed in the cited reference. It is envisioned that this third method would employ a standard, bladder type curing operation but that this method would also, due to the cured configuration of the bead area, have the high stress concentrations in the lower sidewall area of the tire. Additionally, this approach would also have a folded width larger than the other approaches.
All of the tire construction exemplified by these three prior approaches have the tire bead areas stationary or cured in the standard configuration; that is, in substantially the same configuration as they have in their mounted, either inflated or uninflated, shapes. This means that, whether the tire is built on a flat building drum or a contour drum, the tire bead areas are stationary or fixed and attain the shape they will have when the tire is mounted on the rim, either inflated or uninflated, prior to curing and are cured in substantially this shape or configuration. In the contour drum building method, this configuration is obtained on the building drum with little movement of the body ply ends in the bead area during the shaping operation prior to curing. In the flat drum method, this configuration is obtained during the shaping operation prior to the curing by the movement of the body ply ends around the wire bead bundles while the rubber in the tire is still plastic (unvulcanized) and not elastic (vulcanized), as occurs in the curing operation. The above represents standard methods and configurations as are well known in the art.
This standard, preshaped, stationary bead area in the cured tire is an integral part of each of the prior art approaches (see the Figure in U.S. Pat. No. 3,347,300; FIG. 1 in U.S. Pat. No. 3,347,301; U.S. Pat. No. 3,347,964; FIG. 1 of U.S. Pat. No. 3,657,039 and FIG. 1 of U.S. Pat. No. 3,833,042 for examples of the tire bead area after curing). The prior art approaches also demonstrate use of the standard, preshaped bead area in their mounted, uninflated configurations (see the Figure in U.S. Pat. No. 3,347,300; FIG. 2 in U.S. Pat. No. 3,347,301; FIG. 4 in U.S. Pat. No. 3,657,039; FIG. 4 in U.S. Pat. No. 3,833,042 and the Figure in U.S. Pat. No. 3,610,310.) Finally, all the prior art approaches demonstrate the stanard approach that the bead area undergoes no substantial change on inflation from its uninflated shape to its inflated, operable shape (see the Figure in U.S. Pat. No. 3,347,300; FIG. 2 in U.S. Pat. No. 3,347,301; FIG. 2 in U.S. Pat. No.3,657,039; FIG. 2 in U.S. Pat. No. 3,833,042; FIG. 6 in U.S. Pat. No. 3,540,510 and the Figure in U.S. Pat. No. 3,610,310).
The tire and tire and rim combination of this invention depart from the prior art method of curing the tire bead area in the shape it will have when the tire is mounted on the rim and inflated. In this invention the tire is cured with the bead area in a configuration different from its operable, inflated shape. In this invention the mounted, uninflated shape of the bead areas are substantially similar to the cured shape but these are substantially different from the operable shape, mounted and inflated.
This configuration change from cured, mounted shape to inflate shape occurs in the vulcanized tire where the location of the body ply cords are fixed by the vulcanization of the rubber in the tire. It is accomplished by a rotation of the tire body about the central core of the tire bead when the tire is inflated to its operable shape from its mounted, uninflated shape. This rotation of the tire body results in a displacement in the bead area of approximately 90.degree..
Specifically, the tire of this invention is cured with its bead areas and lower sidewall areas in a plane substantially parallel to the axis of the tire when it is in its operable configuration. The tire is mounted on the rim with the bead areas and lower sidewall retained in this same basic configuration prior to inflation. This configuration eliminates the hump or bend immediately adjacent the bead that is standard in all prior tires having collapsible features. The elimination of this enables the tire of this invention to have the facility of attaining a smaller overall diameter in its collapsed, uninflated configuration. This is due to the fact that the bead area and lower sidewall area of the tire of this invention are permitted to rest directly on the rim base for a substantial distance, whereas in the prior art tires the hump in the bead area does not permit this feature. Additionally, the elimination of the hump removes the severe stresses that are created in the lower sidewall areas of the prior tires by the buckling that occurs in this area when the tire is inflated. This is due to the fact that the entire bead area of the tire of this invention rotates to permit the lower sidewall to move during the inflation stage, whereas in the prior art tires the bead area is stationary or fixed and the lower sidewall area must move in relation to this fixed, bulky area.
Any stresses created in the lower sidewall and bead area of the tire of this invention during the inflation stage are created in the bead area which is then firmly fixed to the rim. These stresses, if any, are created by the rotation of the bead areas about the center of the bead bundle and, as such, are not detrimental to the performance of the tire. Any tire bead structure which permits this action in the bead area is within the scope of this invention.
The preferred method for obtaining this rotation in the bead area embodies the use of what is known in the art as a cable bead construction. One type of cable bead construction contains a solid metal wire core (see U.S. Pat. No. 1,386,072) with individual strands of smaller bead wires helically wrapped around the core. The standard bead bundle construction contains plies of parallel wire which are wrapped around each other. The cable bead construction permits a rotation of the smaller, external bead wires about the heavier wire core so that the rotation is internally in the bead wire bundle as opposed to the fabric rotating about the bead bundle externally as in the standard construction. Beads of this type are known and have been utilized in tire constructions taking advantage of the internal rotation in the bead bundle when the tire is in its uncured state. Such a rotation permits a tire to be constructed wherein there is little displacement of the tire body fabric ends in relation to the body fabric in the bead area during the relocation of the tire body fabric which occurs in the change to the toroidal shape from the flat shape or shaping prior to curing. This feature has been utilized solely with standard, stationary tire bead areas wherein the tire bead areas are cured in the position they will have when the tire is mounted and operable and has not been utilized in cured tires.
In the present invention this cable bead rotation concept is used after the curing operation in a vulcanized tire. This permits the tire to be mounted on the rim with the bead area of the tire in a non-rotated position with the rotation occurring during the inflation step from the folded tire shape to the toroidal shape by the rolling of the bead area of the tire about the center of the bead bundle. This permits the tire to be physically located on the rim in a different configuration in its uninflated state as compared to its inflated state. Such a configuration may result in a smaller tire diameter in its mounted, uninflated and folded shape than has been previously possible.
The tire of this invention may alternatively contain a bead bundle that is comprised of an aramid type fabric. Bead bundles of this type are more flexible than any of the known wire bead bundle constructions, yet give sufficient strength to maintain the integrity of the tire during its operation. Bead bundles of this type permit the movement of the bead area of the tire about the center of the bead bundle to yield the same result as is described above with the cable bead type construction.
It is an object of this invention to obtain a tire which may be folded when uninflated to occupy less space than a standard tire of thesame inflated dimensions.
It is a further object of this invention to obtain a foldable tire and rim combination that conserves space when the tire is uninflated as compared to a standard tire of the same inflated dimensions.
It is a further object of this invention to obtain a tire in which the bead areas of the tire are cured in a configuration which permits the bead area and the lower sidewall area to rest on the base of the rim when the tire is mounted and uninflated.
It is a further object of this invention to obtain a tire in which the bead area is molded in a configuration different than the configuration that the bead area obtains when the tire is mounted and inflated.
It is a further object of this invention to obtain a tire in which the bead area is constructed to permit a rotation or rolling of the bead area of the tire around the center of the bead bundle during inflation of the tire to its operable shape.
It is a further objective of this invention to obtain a foldable tire that may be manufactured in a process with bladder-type curing.
It is a further object of this invention to obtain a foldable tire that is free from a high degree of prestress in the lower sidewall area when it is mounted and inflated in its operable condition.
Other objects of this invention will be evident from the disclosure.